PSL4#24

$\text{we have essentially 4 entities given: ma, ka, la, and a}\\ \text{having placed the 3 pairs there are 4 slots in which the a can be placed}\\ \text{the 3 pairs can be arranged in $3!$ ways and then there are 4 ways to place the a, for a total of}\\ N=3!\cdot 4 = 6\cdot 4 = 24$