Let's say you made a forecast for Week $4$ and Week $5$ based on a $2-$week simple moving average. What is the difference between the forecast for Week $4$ and the forecast for Week $5?$

Week

Income

$1$

$420$

$2$

$510$

$3$

$400$

$4$

$540$

$5$

$500$

$6$

Group of answer choices

$50$

$15$

$40$

$25$