I made a simple model several weeks ago which led to a conjecture, which I have been unable to prove thus far.

Problem:
Given constants s and h such that
0<s<h/2,
functions p(x) and C_{i}(x) ( i\in\{1,2\}) such that
p(z)>0,p'(z)<0,p''(z)>0
C_{i}'>0,C_{i}''>0
and values
\exists x,y:\qquad-p'(x+y)=\frac{C_{1}'(x)}{h/2}=\frac{C_{2}'(y)}{s}
\exists x^{*},y^{*}:\qquad-p'(x^{*}+y^{*})=\frac{C_{1}'(x^{*})}{h-s}=\frac{C_{2}'(y^{*})}{s}.

Prove or disprove that the following always holds:
h(p(x+y)-p(x^{*}+y^{*}))>C_{1}(x^{*})-C_{1}(x)+C_{2}(y^{*})-C_{2}(y)

Best attempt so far:
h(p(x+y)-p(x^{*}+y^{*}))>h(x+y-x^{*}-y^{*})p'(x^{*}+y^{*})
=h(x^{*}-x+y^{*}-y)(-p'(x^{*}+y^{*}))(\frac{h-s}{h}+\frac{s}{h})
=(x^{*}-x+y^{*}-y)(C_{1}'(x^{*})+C_{2}'(y^{*}))
I've tried using other inequalities, but I always managed to find counterexamples in Mathematica.
So far, I have not found a counter examples for (x^{*}-x+y^{*}-y)(C_{1}'(x^{*})+C_{2}'(y^{*}))>C_{1}(x^{*})-C_{1}(x)+C_{2}, so I think I'm in the right direction.
Perhaps someone knows of an application which can search for counterexamples given such conditions?

Any suggestions would be very, very, very much appreciated.