.banner {
    width: 100%;
    height: 150px;
    background-size: cover;
    background-repeat: no-repeat;
   
}
@media screen and (min-width:768px){
    .banner{
        height: 200px;
    }
    
}
@media screen and (min-width:1200px){
    .banner{
        height: 300px;
    }
}