Rhianna is baking a cake and some cookies for a party. She used 4 1/2 cups of flour for the cake. For each tray of cookies, she needs 2 1/2 cups of flour. She decides to use at least 15 cups of flour for the cake and the cookies. Assuming she can make fractional trays of cookies, how many trays, x, can she make? Select the inequality that includes the minimum number of trays of cookies Rhianna can make.