请各位看看本C语言的问题

问题遇到的现象和发生背景

C语言vs编写

用代码块功能插入代码，请勿粘贴截图

#include
int main(void)
{
int a, b;
double jiage;
char op;

scanf("%d %d", a, b);
op = getchar();

if (b = 90) {
    jiage = 6.95 * a;
    printf("%.2f", jiage);
} else if (b = 93) {
    jiage = 7.44 * a;
    printf("%.2f", jiage);
} else if (b = 97) {
    jiage = 7.93 * a;
    printf("%.2f", jiage);
} else ;
return 0;

}

scanf("%d %d",&a, &b)
if (b == 90)

判断相等用双等号==
最后一个else去掉