Pythagorean theorem:
a^2+b^2=c^2 (C^2 always is the hypotenuse)
21^2+b^2=29^2
441+b^2=841
841-441=400
square root of 400 is 20
Your answer is 20
Monthly amount, M = $102×4 = $408.
Also, yearly amount, Y = M×12 = $408×12 = $4896
It is given that 25% of the cost is contributed by Marcus.
Amount Marcus paid

Therefore, his employer contribution annually for coverage is $( 4896 - 1224)=$3672.
Hence, this is the required solution.