i need help building this program with "if else" comands

We will be determining the postage cost for regular or large envelopes not weighing more than 3 ounces. The chart below shows the rates. Large 1.00 1.15 1.30 Weight Not Over (oz.) Regular 0.55 0.70 0.85 2 Your program will input values until a weight less than 0 or greater than 3 ounces is entered. Postage Calculations What is the weight of the letter, in ounces? 0.3 , What is the size of the letter? (L large, R = regular) r The postage for a regular letter weighing 0.30 ounces is 0.55 What is the weight of the letter, in ounces? 0.6 what is the size of the letter? (L large, R regular) l The postage for a large letter weighing 0.60 ounces is $ 1.00 What is the weight of the letter, in ounces? 1.5 What is the size of the letter? (L large, R - regular) The postage for a large letter weighing 1.50 ounces is s 1.1 what is the weight of the letter, in ounces? 2.1 hat is the size of the letter? (L large, R regular) r The postage for a regular letter weighing 2.10 ounces is 0.85 What is the weight of the letter, in ounces? 9 The total cost of postage is 4.50