To save for retirement, Ed is investing 12.236 thousand dollars this year. Write the function R(t) that shows the stream of money flowing into Ed's investment account under each of the following circumstances. Assume a continuous income stream. Do NOT round any values. (a) Ed continues to invest the same amount each year for the next 20 years. R(t) = thousand dollars per year (b) Ed increases his investment by 4.42 thousand dollars per year over the next 20 years. R(t) = thousand dollars per year (c) Ed increases his investment by 4.42% each year over the next 20 years. R(t) = thousand dollars per year