Travel calculation

Sam is going on a road trip and needs to apply for inter-district and inter-state travel e-passes. It takes A minutes to fill each inter-district e-pass application and B minutes for each inter-state e-pass application.
His journey is given to you as a binary string S of length N where 0 denotes crossing from one district to another district (which needs an inter-district e-pass), and a 1 denotes crossing from one state to another (which needs an inter-state e-pass).

Find the total time Sam has to spend on filling the various forms.
        
       Input:-3
2 1 2
00
2 1 1
01
4 2 1
1101
       Input Description: The first line of The input contains a single integer T denoting The number of test cases. The description of T test cases follows.
-each test case contains two lines of input.
-first line contains three space separated integers N,a and B.
-second line contains The string S. 
       Output: 2
2
5
       Output Description: For each testcase, output in a single line the total time Sam has to spend on filling the various forms for his journey. 
       Constraints: 1<=T<=10 
2
1<=T<=10^2
1<=N,A,B<=10^2
Si ? { ? 0 ? , ? 1 ? }

       Explanation: Test case 1: Sam needs total 2 inter-district e-passes, and he will be filling them in total 1?2=2 minutes.

Test case 2: Sam needs total 1 inter-district e-pass, and 1 inter-state e-pass so he will be filling them in total 1?1 + 1.1 = 2 minutes.

Test case 3: Sam needs total 1 inter-district e-pass and 3 inter-state e-passes, and he will be filling them in total 2?1+1?3=5 minutes.