Write a SQL (in PostgresSQL) function that accepts a principal mortgage amount, an annual percentage rate (APR), and the number of years a mortgage will be paid back over. Calculate the associated monthly mortgage payment according to the following annuity formula:

A = P (i + in ) (1+i) 1

where:

A = Monthly Payment Amount P = Principle (Initial) Mortgage Amount i = APR / 12 = Monthly Interest Rate n = years * 12 = Total Number of Payments

Be sure to specify that data types of the input arguments have enough significant digits to account for realistic mortgage amounts