.mainGrid {
  display: grid;
  grid-template-columns: 300px 300px 300px 300px;
  grid-template-rows: 300px 300px 300px;
  grid-gap: 1rem;
}

.mainGrid img {
  object-fit: cover;
  width: 100%;
  height: 100%;
  
}
.mainGrid div{
    background: #e8e8e8;
    padding:10px;
}

.mainGrid .item-a {
  grid-row: 1 / 3;
}

.mainGrid .item-b {
  grid-column: 3 / 5;
  position: relative;
}

.mainGrid .item-c {
  grid-row: 2 / 4;
}

.mainGrid .item-d {
  grid-column: 3 / 5;
}