Also fixed var in description of cloudformation command

Author: Sun

01-path-basics/102-your-first-cluster/readme.adoc

@@ -74,7 +74,7 @@ To launch your worker nodes, run the following CloudFormation CLI command:
                      {\"ParameterKey\": \"VpcId\", \"ParameterValue\": \"${EKS_VPC_ID}\"},
                      {\"ParameterKey\": \"Subnets\", \"ParameterValue\": \"${EKS_SUBNET_IDS}\"}]"
 
-The `AWS_MASTER_STACK`, `EKS_WORKER_AMI`, `EKS_VPC_ID`, `EKS_SUBNET_IDS`, and `EKS_SECURITY_GROUPS` environment variables should have been set during the link:../101-start-here[Cloud9 Environment Setup].
+The `AWS_STACK_NAME`, `EKS_WORKER_AMI`, `EKS_VPC_ID`, `EKS_SUBNET_IDS`, and `EKS_SECURITY_GROUPS` environment variables should have been set during the link:../101-start-here[Cloud9 Environment Setup].
 
 Node provisioning usually takes less than 5 minutes. You can query the status of your cluster with the following command. When your cluster status is `CREATE_COMPLETE`, you can proceed.