Required information NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part. Let Pri) be the statement that a postage of n cents can be formed using just 4-cent stamps and 7-cent stamps. The parts of this exercise outline a strong induction proof that Pn) is true for n 2 18. Show that the statements P118), 2(19), P20), and P121) are true, completing the basis step of the proof. (You must provide an answer before moving to the next part.) P18) is true, because 18 cents of postage can be formed from P19) is true, because 19 cents of postage can be formed from P120) is true, because 20 cents of postage can be formed from P121) is true, because 21 cents of postage can be formed from 14-cent stamps and 34-cent stamps and 4-cent stamps and 4-cent stamps and 27-cent stamps. 17-cent stamps. 7-cent stamps. 7-cent stamps.