First calculate the hourly rate, which is the difference of cleaning 2 and 1 rooms:
175-125=50
then calculate the initial value by subtracting the hourly rate from the "1 room" cost:
125-50=75
The initial cost might be something like driving to the place (which is only necessary once), while the rate covers work time or cleaning utensils used.
P,Q,R can't be 0, because their product is nonzero. Either of S and T could be 0, but the third one only works if S is 0.
(DVD player+ TV)= 49.36+705.20= 754.56
754.56/12=62.88
She will have to pay $62.88 each time
