LMP would be 74 degrees and NMP would be 63
The ratio would be 4:6 because 4 of the marbles are pink and 6 (the rest) are blue
Marginal Revenue is defined as the revenue generated with respect to increase in sale of another extra unit of product.
So we will calculate Marginal Revenue equation by finding the change in Revenue with respect to change in Quantity.
Given the Total Revenue Function as:-

Differentiating Total Revenue function (Tr) with respect to quantity (q):-
So Marginal Revenue equation will be, 
Answer:
a) 12.5 hours and b) 4 water pumps
Step-by-step explanation:
a) If 6 wp is filled in 15 hours, then:
5 wp is filled in X hours
X hours = (5*15)/6
X = 12.5 hours.
b) If 6 wp is filled in 15 hours, then:
Ywp is filled in 9 hours
Ywp = (9*6)/15
Ywp = 3.6 aprox 4 water pumps