Assuming that their exam success is independent then
P(both fail) = 1/4 x 2/5 = 2/20 or 1/10
B. is the answer hope I got it right: )

As, 

=0.301029+0.845098+1.13943
=2.26007
=2.260(approximate)
$450 per week earns you $450 total per week, for $<span>23,400 total
$115 per week earns you that plus 9.5% of $125,000, which is $</span>11,875, plus $5,980 which is $<span>17,855 total
There is a $</span><span>5,545 difference, making the $450 a week a better deal</span>