A marketing researcher conducted a multiple regression analysis to explain how much customers spend on a company's products (Amount Spent) as a function of four customer characteristics/variables:annual salary (Salary), number of children (Children), age (Age), and location (Location; rural or urban). Use the two partial ANOVA tables from the regression analysis below to determine how much additional variation (as a percentage) in Amount Spent can be explained by Salary and Children, together, over-and-above Age and Location:

MODEL 1:Amount Spent = f(Age, Location)

SST = 76,200SSE = 56,400MSR = 9,900

MODEL 2:Amount Spent = f(Age, Location, Salary, Children)

SST = 76,200SSE = 15,600MSR = 15,150