convert varchar to int in sql

Question

Hai,

 

         i have 2 columns in table are

 

column name datatype is varchar

column Amount is nvarchar

     

Name	Amount
Karthikeyan R	11
Karthikeyan R	51
Mohammedhussain T M	19
Mythili V	37
Rangaraj C	145- $4358.14

                 

                 i want sum the amount against name.plz help me