Odesolve Error: Variable is Undefined?

Hello All, I am a chemical engineering student and a first time MathCAD user.

I am currently running MathCAD 2.0 Prime, and to be blunt, I have no clue what I am doing when it comes to solving a system of ODE. I have attached a worksheet with a problem that I am trying to solve for my Process course. I have reproduced a correct solution in a CAS that I am more familiar with, but have no dice with MathCAD 2.0 Prime. The odesolve function is spitting a "Variable is undefined, check that the label is set correctly" message at me. I haven't the slightest clue how to fix this error. Could a more briefed user please impart some knowledge onto me so I can learn how to solve a system of ODEs in Mathcad?

Thanks,

Alex Holburn