Read this excerpt from Frida Kahlo by Hedda Garza.
Aside from the caricatures she had scribbled in school and the drawings for Fernando Fernández, Kahlo had never paid much attention to art. She began teaching herself from art books, studying the works of the Italian Renaissance artists and experimenting with the colors in her father's paint box. She painted portraits of visitors and relatives who were willing to sit and pose for her and gave the paintings away as gifts.

Garza's purpose is
to entertain young children with Frida Kahlo's adventures; her tone is informal.
to inform a general audience about Frida Kahlo's life and art; her tone is formal.
to persuade art buyers to collect Frida Kahlo's paintings; her tone is informal.
to inform art professors about Frida Kahlo's technique; her tone is formal.