Write out what is meant by the following: {{MATH_40}} {{CMD_41}} The index variable here is written as {{MATH_42}} instead of {{MATH_43}}. That's ok. The most common variables to use for indexes include {{MATH_44}}, {{MATH_45}}, {{MATH_46}}, {{MATH_47}}, and {{MATH_48}}. {{ENV_49}} This is equal to: {{ENV_50}} {{CMD_51}} {{CMD_52}}