certain superstores will often price match or even beat a competitor's price by 10%.the function g(x)=0.90x represents the sale price of a piece of merchandise at such a superstore.the function f(x)=0.13x represents the HST owed on a purchase with a selling price of x dollars.write a function that represents the HST owed on an item with a price tag of x dollars after it has been beaten by 10%

Question

certain superstores will often price match or even beat a competitor's price by 10%.the function g(x)=0.90x represents the sale price of a piece of merchandise at such a superstore.the function f(x)=0.13x represents the HST owed on a purchase with a selling price of x dollars.write a function that represents the HST owed on an item with a price tag of x dollars after it has been beaten by 10%
how much HST would be charged on a 39.99$ purchase if this price is also lowered by 10% first.