The square root of pi is 1.77245385091.
for all of them its base times height
v=bh
1) (8*6/2)*9.5=228
2) (4.5/2)^2 *8= 40.5
3) (3.3* 8.3/2) *5.4= 74.0
4) ((3.2+4.8)/2)* 2.7 *4.4= 47.5
18 x 40 = 720 per week.....720 x 4 = 2880 per month earnings
net pay = 0.72(2880) = 2073.60 <=== cash inflow.
how much he spends per month is his cash outflow.