Did you tried something like:
In the total course ( you have to do it manuallly editing the formula) :
=if( [ [task1] ]="S" and [ [task2] ]="S", S, NYS )
More info: https://docs.moodle.org/36/en/Grade_calculations#Example_calculations and
In the total course ( you have to do it manuallly editing the formula) :
=if( [ [task1] ]="S" and [ [task2] ]="S", S, NYS )
More info: https://docs.moodle.org/36/en/Grade_calculations#Example_calculations and
Also if and is not implemented in moodle you could do some nesting ( i put an example with two tasks:
=if( [ [task1] ]="S", if( [ [task2] ]="S", S, NY ), NYS )
With three:
=if( [ [task1] ]="S", ( if( [ [task2] ]="S", ( if( [ [task3] ]="S", S, NYS), NYS, NY ), NYS )