Previous Problem List Next (1 point) A manufacturer produces bolts of a fabric with a fixed width. A quantity q of this fabric (measured in yards) that is sold is a function of the selling price p (in dollars per yard), so we can write q = f(p). Then, the total revenue earned with selling price p is R(p) = pf (p). Find R' (20), given f(20) = 10000, and f' (20) = -250. (What does this mean?) R' (20) =