The demand function for a particular product is given by D(x)=−0.75x2+5x+50‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾√
D
(
x
)
=
−
0.75
x
2
+
5
x
+
50
dollars, where x is the number of units sold. What is the marginal revenue when 11
11
items are sold? Round your answer to 2 decimal places.