You should NOT use global assignments ( = ), but boolean equality to define the equations in your solve block. Type [CTRL =] to get those. They show as a bold equals sign ( = ).
1) You have to only use the function names without the argument parenthesis (use "C" and not "C(t)")
2) You have only 5 equations but 6 functions to solve for.
you should provide the f (t); what I chose is a convenience function. I do not believe that Mathcad is able to determine f (t) as an unknown knowing only its initial condition.
That very blurry picture shows a graph with only 4 traces. That's 4 functions, not 6.
Are you sure you have entered the complete set of ODE's, required for solving the 6 functions that you are trying to find?