Answer:
unknown, because the cost of the sandwich, a drink and a bag of chips where not listed in the question
₇P₅ is a permutation. you can find this setting in the statistics menu of your scientific calculator (i think).
If you don't have a scientific calculator, you can use the following formula:
nPr = 
₇P₅ = 
= 
= 
= 7 * 6 * 5 * 4 * 3
= 2520
Answer: C
It is 110
Slope of the line is 10x So you will earn 110$ in 12 hours.