5. (a) Rahat has built up a mini library in his house. He has five shelves - one for Bangla novels, one for English novels, one for Maths and Science, one for current affairs, and one for comics. What is the minimum number of books Rahat must have if he has at least 150 books of the same category? [2] (b) Grameenphone has recently been allowed to use the series 013 along with 017 in the moble phone numbers it can provide. There are a total of 11 digits in its mobile numbers, where each the remaining 8 digits are between 0 and 9 . How many mobile phone numbers can Grameenphone provide? (c) Wordle is a new game where a player have to guess a five-letter word in six chances. In each chance, some letters are eliminated. Zinia was playing this game, and after five chances, she realized that the letters A, C, D, E, H, K, L, O, S, T, U and Y are eliminated. How many possible valid answers are remaining? [3]