Lieutenant Commander Data is planning to make his monthly $($every $30$ days$)$ trek to Gamma Hydra City to pick up a supply of isolinear chips. The trip will take Data about four days. Before he leaves, he calls in the order to the GHC Supply Store. He uses chips at an average rate of nine per day $($seven days per week$)$ with a standard deviation of demand of five per day. He needs a $90($ninety$)$ percent service probability. When picking values from the normal distribution table, make sure to choose the closest number and do not approximate.

a$.$ If he currently has $25$ chips in inventory, how many should he order?

b$.$ What is the most he will ever have to order?