The following table shows the data for the sales of tennis rackets at a store for $4$ consecutive months. Find the forecast error in month $4$ using a $3-$month moving average.

a$.$ The forecast error in month $4$ is more than $15.$

b$.$ The forecast error in month $4$ is less than or equal to $5.$

c$.$ The forecast error in month $4$ is more than $5$ but less than or equal to $10.$

d$.$ The forecast error in month $4$ is more than $10$ but less than or equal to $15.$