Lucky Sum

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Chef loves lucky numbers. Everybody knows that lucky numbers are positive integers whose decimal representation contains only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not.
Chef also use term "lucky sum". Lucky sum is an operation between two integers. Let the first integer is A, A[i] equals ith digit of A (0base numeration, from right to left) and the second integer is B, B[i] equals to ith digit of B. Then the lucky sum of A and B is equal to C, C[i] = max(A[i], B[i]). If i is greater than or equal to size of integer, the ith digit is equal to 0. For example, the lucky sum of 47 and 729 equals 749, the lucky sum of 74 and 92 and 477 equals 497.
Chef has an array W of integers. Find a number of nonempty subsequences of W such that the lucky sum of integers in that subsequences is a lucky number.
Subsequence of W is created by erasing some number (probably zero) elements from W.
Input
First line contains one number T, number of test cases. Each test is formed as follows: first line contains integer n  number of integers in W, next line contains n integers  array W for corresponding test.
Output
For each T test cases print one integer  result for the corresponding test.
Constraints
1 <= T <= 10
1 <= n <= 50
1 <= Wi < 10^9
Example
Input: 2 2 4 7 3 43 87 44 Output: 3 2
Author:  witua 
Tester:  laycurse 
Editorial  http://discuss.codechef.com/problems/LUCKY3 
Tags  jan12, medium, witua 
Date Added:  21112011 
Time Limit:  1.43449 sec 
Source Limit:  50000 Bytes 
Languages:  C, CPP14, JAVA, PYTH, PYTH 3.6, CS2, PAS fpc, PAS gpc, RUBY, PHP, GO, NODEJS, HASK, SCALA, D, PERL, FORT, WSPC, ADA, CAML, ICK, BF, ASM, CLPS, PRLG, ICON, SCM qobi, PIKE, ST, NICE, LUA, BASH, NEM, LISP sbcl, LISP clisp, SCM guile, JS, ERL, TCL, PERL6, TEXT, CLOJ, FS 
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