Question 987859
C(6,20 )  is a point on the line which is part of
a 3-D plot, C( x,y ), and the form is:
C( x,y ) = C( 6,20 ), so {{{ x = 6 }}}, {{{ y = 20 }}}
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{{{ C( x,y ) = 2000 + 50x + 70y }}}
{{{ C( 6,20 ) = 2000 + 50*6 + 70*20 }}}
{{{ C( 6,20 ) = 2000 + 300 + 1400 }}}
{{{ C( 6,20 ) = 3700 }}}