Chess pieces are often considered to have a point value for roughly evaluating a position. Write a function called material_count that takes a single string representing all the pieces a player has (one character per piece) and returns their total material count. The pieces with a point value are:

• P (pawn): 1 point
• B (bishop): 3 points
• N (knight): 3 points
• R (rook): 5 points
• Q (queen): 9 points

You may assume that there are no other letters in the string.

For example, given PNR you would return 9: 1 from the pawn, 3 from the knight, and 5 from the rook.