Question: maple programming

i want to know that is ther any procedure or builtin functin which return the exponent of a variable.For example if i have a variabl x^2 result will be 2.and also i want to know the procedure by which if i have two lists of variables we can compare there type of variables and cobine the coefficients of same variables.For example >s:=[v1,2*x^2*y,v2,1*x*y^2,v0,3*x^3]; >p:=[a*x^3,b*x*y^2,c*x^2*y]; i want to get result v1,2+c ,v2,1+b, v0,3+a how can i get this result any body help me
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