Create a SIN number validator <p>I am creating a C program which tests if a user has entered a valid SIN number. Here is what I have done so far:</p> <pre><code>#include &lt;stdio.h&gt; int main(void) { int num1; printf("Enter your SIN number: \n"); scanf("%d", &amp;num1); } </code></pre> <p>SIN number is a 9 digit long number. To see if it is valid, I want to multiply the SIN number like this: </p> <pre><code>add SIN number with 121 212 121. 123 456 789 121 212 121 </code></pre> <p>How would I do this part in C programming language?</p>