please see attached image. For part b i want to know how to solve it by using MRS

Let Charlie's utility function be U{C, L) = C: + L2. Suppose he has T hours to split between work and leisure and he has no nonlabor income. (a) What combinations of C and L give Charlie a utility of 4? Is there any geometric interpretation of the equation you derive? 1What does this mean for optimal solutions? [2 points]I (b) Derive Charlie's Optimal choice of canSmnptiOn and leisure as a function of the wage and T. (2 points} (c) What is Charlie's reservation wage? [2 points) (d) If Robert's utility function is U(C, L) = C2 + 9L2, is his reservation wage higher or 10wer than Charlie's? [1 point}