Definition: You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.
Input: Question: In how many different ways can the letters of the word MISSISSIPPI be arranged if the vowels must always be together?

 Option A: 48

 Option B: 144

 Option C: 210

 Option D: 420

 Option E: 840

Option E