The requirements specification of a product begins with this sentence:
"The xyz system will provide many new user functions. These must be easy for our operators to use and tolerant of user input errors. These new functions must also be easy to learn. Because of very high transaction rates and limited processing power, the software design must be very efficient. The system must be available as close to 24x7 as possible.
Which three ISO 25010 major quality characteristics should be tested for possible defects with this implementation?