Please help its due soon ill give brainlest

The last time i bought this product , it cost $20.00 but it looks like it cost 29. 60 today? what is the increase

The average number of vehicles waiting in line to enter a parking lot can be modeled by the function f left parenthesis x right x squared over 2 left parenthesis 1 minus x right parenthesis endfraction , where x is a number between 0 and 1 known as the traffic intensity. find the rate of change of the number of vehicles waiting with respect to the traffic intensity for the intensities (a) xequals0.3 and (b) xequals0.6.

Ineed in figuring out this problem.