How to apply regular function to df third column?

Question

I have df that currently has two columns df[['sys1','dia1']]

I created this function (the parameters are d= df['dia1'] and s = df['sys1'] :

Now i am trying to create a third column by using this function. It would look like this:

df['FirstVisitStge'] = df['FirstVisitStge'].apply(classify)

I am getting an error. I even tried using predefined parameters in the function and still getting an error. What am i doing wrong?

def classify(d,s):
    if (d>=90 & d<100 & s<160) or (s >= 140 & s < 160 & d < 100):
        return 'Stage 1'
    elif (s >= 160 & s <180 & d <110) or (d >= 100 and d < 110 and s > 180):
        return 'Stage 2'
    elif s >= 180 or d >= 110:
        return 'hypertensive crisis'
    else:
        return 'NA'