Use multiple conditions for count in terraform ternary operations using elseif

Terraform
1

I am trying to get terraform to create a resouce based on the count conditon as below, i cant get my head around the syntax, it should be something like below:

count = “${var.size[terraform.workspace] == "big" ? && local.ips[terraform.workspace] != “<none>“} then 10
elseif
${var.size[terraform.workspace] == "small"  && local.ips[terraform.workspace] != “<none>” } then 20
else 0