Which of the following is a collateral promise that needs to be in writing to be enforceable? Group of answer choices All of these are collateral promises. A father tells a merchant to deliver a computer to his daughter and says, "Send me the bill. I'll pay for it." A mother tells a merchant to extend $1,000 worth of credit to her son and says, "If he doesn't pay, I will." Andrew promises Donald that if Donald cannot pay his bills, Andrew will.