Layla works at an electronics store as a salesperson. Layla earns a 3% commission on the total dollar amount of all phone sales she makes, and earns a 4% commission on all computer sales. How much money would Layla earn in commission on a day that she sold $1800 worth of phones and $1500 worth of computers? How much money would Layla earn in commission on a day that she sold $p worth of phones and $c worth of computers?