Answer
$26$
Work Step by Step
There are 5 stocks with yields above 3.5%.
If the portfolio contains exactly 4 of these, we can choose these 4 out of the 5 in $C(5,4)=5$ different ways, and we can choose the last stock out of 5 (with yields below 3.5%) $C(5,1)=5$ different ways. This gives $5*5=25$ portfolios.
If the portfolio contains five stocks with yields above 3.5%, that can be only 1 way (Because there are 5 stocks with such yields).
So the total number of different portfolios is $25+1=26$
