Answer:
a)
The proportion of contracts involved at most five bidders is 0.667.
The proportion of contracts involved at least five bidders is 0.51.
b)
The  proportion of contracts involved  between five and 10 inclusive bidders is 0.5.
The  proportion of contracts involved  strictly between five and 10 bidders is 0.304.
Step-by-step explanation:
No. bidders    No. contracts     Relative frequency of contracts
2                         6                       6/102=0.0588
3                         20                     20/102=0.1961
4                         24                     24/102=0.2353
5                         18                       18/102=0.1765
6                         13                        13/102=0.1275
7                          7                          7/102=0.0686
8                          5                          5/102=0.049
9                          6                          6/102=0.0588
10                         2                           2/102=0.0196
11                          1                            1/102=0.0098
Total                  102
a)
We have to find proportion of contracts involved at most five bidders.
Proportion of at most 5= Relative frequency 2+ Relative frequency 3+ Relative frequency 4+ Relative frequency 5
Proportion of at most 5=0.0588+ 0.1961+0.2353+0.1765
Proportion of at most 5=0.6667
The proportion of contracts involved at most five bidders is 0.667.
proportion of at least five bidders= proportion≥5= 1- proportion less than 5
Proportion less than 5=0.0588+ 0.1961+0.2353=0.4902
proportion of at least five bidders=1-0.4902=0.5098
The proportion of contracts involved at least five bidders is 0.51
b)
We have to find proportion of contracts involved  between five and 10 inclusive bidders.
Proportion of contracts between five and 10 inclusive= Relative frequency 5+ Relative frequency 6+ Relative frequency 7+ Relative frequency 8+ Relative frequency 9+ Relative frequency 10
Proportion of between five and 10 inclusive=0.1765 +0.1275 +0.0686 +0.049 +0.0588 +0.0196
Proportion of between five and 10 inclusive=0.5
The  proportion of contracts involved  between five and 10 inclusive bidders is 0.5
We have to find proportion of contracts involved  strictly between five and 10 bidders.
Proportion of contracts strictly between five and 10=  Relative frequency 6+ Relative frequency 7+ Relative frequency 8+ Relative frequency 9
Proportion of strictly between five and 10=0.1275 +0.0686 +0.049 +0.0588 
Proportion of strictly between five and 10=0.3039
The  proportion of contracts involved  strictly between five and 10 bidders is 0.304.