This paper extends to the multi-assets framework the closed-form solution for options with stochastic volatility derived in Heston(1993) and Ball and Roma(1994). This extension introduces a risk premium in the return equation and considers Wishart dynamics for the process of the stochastic volatility matrix, which is the multi-assets simulation of the model of Cox, Ingersoll, and Ross(1985). This approach is used to extend Merton's model for corporate default to a framework with stochastic liability.