Denote by x the number of cones sold or produced.
Denote by C(x) the total cost.
Denote by R(x) the revenue made.
Denote by P(x) the net profit accumulated.
[tex]C_{T}(x)=C_{fixed}+C_{variable} \: \\ C_{T}(x)=36+0.52x[/tex]
[tex]R_{T}(x)=selling \: price \: x \\ R_{T}(x)=1.4x[/tex]
[tex]P(x)=R_{T}(x)-C_{T}(x) \\ P(x)=1.4x-(36 + 0.52x) \\ P(x)=1.4x - 36 - 0.52x \\ P(x)=0.88x - 36[/tex]
If there exists profit, then P(x) has to be positive.
[tex]P(x) > 0 \\ 0.88x - 36 > 0 \\ 0.88x > 36 \\ x > \frac{36}{0.88} \\ x > 40.90909 \\ x = 41[/tex]
