Answer:
14 boys paid for the full year fee and 4 boys paid for the partial year fee
Step-by-step explanation:
Create a system of equations, where x is the number that paid for the $24 fee and y is the number that paid for the $16 fee:
24x + 16y = 400
x = y + 10
Solve by substitution by plugging in y + 10 as x:
24x + 16y = 400
24(y + 10) + 16y = 400
Solve for y:
24y + 240 + 16y = 400
40y + 240 = 400
40y = 160
y = 4
Then, plug in 4 as y to find x:
x = y + 10
x = 4 + 10
x = 14
So, 14 boys paid for the full year fee and 4 boys paid for the partial year fee.
All triangles angles in the inside add up to 180, so 180-76-72=32
Split up the interval [2, 5] into

equally spaced subintervals, then consider the value of

at the right endpoint of each subinterval.
The length of the interval is

, so the length of each subinterval would be

. This means the first rectangle's height would be taken to be

when

, so that the height is

, and its base would have length

. So the area under

over the first subinterval is

.
Continuing in this fashion, the area under

over the

th subinterval is approximated by

, and so the Riemann approximation to the definite integral is

and its value is given exactly by taking

. So the answer is D (and the value of the integral is exactly 39).