W14 x 53 section is encased in an 18 in x 22 in concrete section

 A W14 x 53 section is encased in an 18 in x 22 in concrete section.  The composite column is 15 ft in length.  In addition to the steel hot-rolled section, 4 #9 bars are placed as shown across the column cross-section.  Determine the design strength, ϕPn, for the composite column