Syntax error in docker-compose build

$docker-compose build
ERROR:yaml.scanner.ScannerError: while scanning a simple key
  in "./docker-compose.yml", line16, column1
could not find expected':'
  in "./docker-compose.yml", line 17, column 5

version: '3'
services:
  app:
    build:
      context:.
      dockerfile:./docker/rails/Dockerfile
    command —bundle exec unicorn_rails-c/coffee_app/config/unicorn.conf.rb
  # command: bundle exec rails -p 3000-b '0.0.0.0'
    ports:
      - '3000:3000'
    volumes:
      - tmp_data: /coffee_app/tmp/sockets
      - .:/coffee_app
    depend_on:
      - db
​
  db:
    build:
      context:.
      dockerfile:./docker/mysql/Dockerfile
    command:--default-authentication-plugin=mysql_native_password
    ports:
      - '3306:3306'
    volumes:
      - db_data: /var/lib/mysql
  nginx:
    build:
      context:.
      dockerfile:./docker/nginx/Dockerfile
    ports:
      - '80:80'
    volumes:
      - tmp_data: /var/tmp/
​
volumes:
  db_data:
  tmp_data: