Question 945209
Use the two points to find the equation of the cost line.
First find the slope.
{{{m=(y[2]-y[1])/(x[2]-x[1])=(1-0.7)/(35-20)=(0.3)/15=0.02}}}
Then use the point-slope form of a line with either point,
{{{y-1=0.02(x-35)}}}
{{{y-1=0.02x-0.70}}}
{{{y=0.02x+0.30}}}
So then when {{{x=30}}},
{{{y=0.02(30)+0.3}}}
{{{y=0.6+0.3}}}
{{{highlight(y=0.9))}}}
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$0.90.