help me solve these

10. {14 Points] HUNTERDM3 4.2.005. Ruth has the following set of refrigerator magnets: (A, B, C, D, E, F, G}. (a) How many different threeletter strings can she form with these magnets? (b) How many different three-letter strings can she form if the middle letter must be a vowel? 11. {-14 Points] HUNTERDM3 4.4.001. A computer generates a random ve-digit string in the symbols A, B, C, ..., Z. (a) How many such strings are possible? (b) What is the probability that the random string contains no vowels (A, E, I, 0, U)? (Round your answer to four decimal places.) 12. [-/4 Points] HUNTERDM3 4.5.001. Look at pseudocode segment below. ysx+x+x+x+x //1inea z