Extended service agreements which run for $3$ more years require that Sifers$-$Grayson provide software maintenance and patches for SCADA systems sold more than fifteen years ago. The engineering workstations used to provide this support take up $500$ sq ft of space in the R&D lab and, due to their reliance on Windows XP$,$ present security vulnerabilities which need to be walled$-$off from the company's internal networks. To get back floor space and to reduce the vulnerabilities presented by Windows XP$,$ the Lab Manager has proposed moving the SCADA support environment to the Cloud. Which of the following cloud computing environments would be the best match for the required software development and testing environment?

Question $1$ options:

Software as a Service

Platform as a Service

SCADA as a Service

Infrastructure as a Service