Independent solution

How to solve this Uniform Distribution question

Setup

Setup

The policyholder retains the smaller of the loss and the deductible.

R=min(X,d),XUniform(0,450)R=\min(X,d),\qquad X\sim\operatorname{Uniform}(0,450)

Model

Model

Split the expectation between losses below the deductible and losses capped at the deductible.

E[R]=0dxdx450+dPr(X>d)\operatorname{E}[R]=\int_0^d x\frac{dx}{450}+d\Pr(X>d)
E[R]=d2900+d(1d450)=dd2900\operatorname{E}[R]=\frac{d^2}{900}+d\left(1-\frac d{450}\right)=d-\frac{d^2}{900}

Compute

Compute

Set the retained mean to the supplied amount and solve the quadratic.

dd2900=56d-\frac{d^2}{900}=56
d2900d+50400=0d^2-900d+50400=0
d=60ord=840d=60\quad\text{or}\quad d=840

Answer

Answer

A deductible above the maximum possible loss is incompatible with a retained mean of 56, so the admissible root is 60.

60(A)\boxed{60\quad\text{(A)}}