Fixed Income - N(-d1) and N(-d2)

CFA Level II Fixed Income
#1

Reading 45 Credit Analysis Models page 267 of the cfa curriculum example 4 does anyone know how the value of N(-d1) and N(-d2) are calculated?

Thank you

#2

You look up d1 and d2 in a standard normal distribution table (such as you have in the back of the Quantitative Methods book).