On 21 January 1981, you take a back sight of the Sun's upper limb as it appears in the scope. The sextant altitude (hs) is 121°31.5'. The index error is 2.5' on the arc. The height of eye is 31 feet (9.3 meters). What is the observed altitude (Ho)?

A
31°06.2'
B
58°53.1'
C
58°12.2'
D
58°03.2'
E