The number of cable TV networks has grown exponentially from 28 in 1980 to 565 in 2010 (Source: National Cable & Telecommunications Association).
a) Using the data for 1980 and 2010, find the value of k, and write an exponential function that describes the number of cable TV networks after time t, in years, where t is the number of years since 1980.
b) Estimate the number of cable TV networks in 2013 and in 2017.
c) At this growth rate, in which year will the number of cable networks be 1500?