We can eliminate “m”, and we are left with “s” and its permutations with “p”, “r” and “i”. This gives us:
s; sp, sr, si, ps, rs, is; spr, spi, sir, and all the permutations of these; spri and all its permutations.
There are 6 each of the 3-letter permutations.
When we add all these together we get: 1+6+3×6+24=1+6+18+24=49.