решите удобным способом:
4x21x25
5x42x4
25x37x4

4 * 21 * 25 = 25 *4 * 21 = 100 * 21 = 21005 * 42 * 4 = 5 * 4 * 42 = 20 * 42 = 20 * 40 + 20 *2 =  800 + 40 = 84025 * 37 * 4 = 25 * 4 * 37 = 100 * 37 = 3700