  We construct a monomorphism from the differential algebra $k\{x\} / [x^m]$ to
a Grassmann algebra endowed with a structure of differential algebra. Using
this monomorphism we prove primality of $k\{x\} / [x^m]$ and its algebra of
differential polynomials, solve one of Ritt's problems and give a new proof of
integrality of the ideal $[x^m]$.
