Independent solution

How to solve this Discrete Random Variables question

Setup

Setup

Treat the combined sales distribution as a mixture of the two office distributions.

p(x)=0.70p1(x)+0.30p2(x)p(x)=0.70p_1(x)+0.30p_2(x)

Model

Model

Compute the combined masses at prices no greater than 165.

p(150)=0.70(0.20)+0.30(0.25)=0.215p(150)=0.70(0.20)+0.30(0.25)=0.215
p(155)=0.70(0.10)+0.30(0.15)=0.115p(155)=0.70(0.10)+0.30(0.15)=0.115
p(160)=0.70(0.05)+0.30(0.15)=0.080p(160)=0.70(0.05)+0.30(0.15)=0.080
p(165)=0.70(0.10)+0.30(0.10)=0.100p(165)=0.70(0.10)+0.30(0.10)=0.100

Compute

Compute

Accumulate the mixture masses and locate the first support value whose CDF reaches one-half.

F(160)=0.215+0.115+0.080=0.410F(160)=0.215+0.115+0.080=0.410
F(165)=0.410+0.100=0.510F(165)=0.410+0.100=0.510
F(160)<0.5F(165)F(160)<0.5\le F(165)

Answer

Answer

The smallest combined selling price with cumulative probability at least one-half is 165 thousand.

165.0(B)\boxed{165.0\quad\text{(B)}}