Read this section, including the table listing leakages and injections. You should be able to write a formula equating the leakages to the injections and place each item into the expanded, comprehensive, and important version of the circular flow model.
Read this article about the simple multiplier. You should be able to use the formula from this article to calculate the multiplier's numeric value given MPC = 0.80. The result suggests an outcome such as income or GDP increases about five times the amount of a change in consumer expenditures, as articulated in the readings.