To find area $ A $ use formula:
$$ A = \dfrac{ a \cdot c \cdot \sin( \beta ) }{ 2 } $$After substituting $ a = 375 $ , $ c = 486.7654 $ and $ \beta = 54.987^o $ we have:
$$ A = \dfrac{ 375 \cdot 486.7654 \cdot \sin( 54.987^o ) }{ 2 } $$ $$ A = \dfrac{ 375 \cdot 486.7654 \cdot 0.819 }{ 2 } $$ $$ A = \dfrac{ 182537.0235 \cdot 0.819 }{ 2 } $$ $$ A = \dfrac{ 149501.8752 }{ 2 } $$ $$ A = 74750.9376 $$