What are the main features of the mechanical teachers and the schoolrooms that Margie and Tommy have in the story?

Explanation

### Step-by-Step Solution:

1. **Introduction to Mechanical Teachers and Schoolrooms:**
- Margie and Tommy, the characters in the story "The Fun They Had," had unique educational setups compared to traditional schools.

2. **Features of Mechanical Teachers:**
- **Big Black Screens:** The mechanical teachers had large black screens where questions and answers were displayed.
- **Slots for Homework and Test Papers:** There were slots in the mechanical teachers where students would insert their homework and test papers.
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